It's true what they say: Your keyboard is crawling with bacteria. Though if you're a woman, you may have less to worry about. In a new study, researchers took swabs of a variety of office equipment in New York, San Francisco, and Tucson. They found more than 500 types of bacteria, most of which normally live on our skin or in our nasal, oral, and intestinal cavities.

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Chairs and phones accumulated the most bacteria, followed by desktops, keyboards, and computer mice. In a few cases, hardy microbes commonly found in hot springs and volcanic islands also appeared in the mix, perhaps tracked into the office following a vacation to St. Lucia or Yellowstone.

New York and San Francisco's bacterial diversity was virtually identical despite their nearly 4700-kilometer divide, while Tucson's microbes were more variable and tended to be heavy on desert soil bacteria in addition to the human-derived species.

San Francisco offices were the least contaminated. And while the offices of men and women had the same types of species, women's offices had on average 10% to 20% fewer of them. Differences in hygiene may be to blame, the team reports online today in PLoS ONE. Men are known to wash their hands and brush their teeth less frequently than women, the researchers write, and are generally "perceived to have a more slovenly nature."